I have signs of pregnancy and my period is supposed to be due in 4days time. when can i do a blood pregnancy test? thanks.

Missed period: If one's normal regular period comes, she is presumed not pregnant and no pregnancy test is needed. A blood pregnancy test can be done any time, but results are only reliable about a week earlier than urine test results. By 3 weeks after sex, both urine pregnancy tests and blood pregnancy tests are very accurate. Patience is a virtue. Just do a home urine test if one's period is several days late.